High pressure paint spray gun



Nov- 27, 1962 R. J. HOSTETTER 3,065,918

HIGH PRESSURE PAINT SPRAY GUN Filed Nov. 3, 1959 gaber/ d flar/e/f eUnited States Patent Ofiice 3,065,918 Patented Nov. 27, 1962 3,065,918HIGH PRESSURE PAINT SPRAY GUN Robert J. Hostetter, Chicago, Ill.,assignor to Stewart- Warner Corporation, Chicago, 111., a corporation ofVirginia Filed Nov. 3, 1959, Ser. No. 850,578 2 Claims. (Cl. 23--575)This invention relates to apparatus for spraying materials such as paintsubjected to high pressures without admixture with air.

In the paint spraying field, a serious problem of spray nozzlecontamination has existed without appreciable alleviation as far as isknown. In spraying paints and other similar materials on surfaces bymeans of power equipment, it becomes necessary to utilize nozzles havingvarious types of small cross-section orifices. The orifice shape andrelated structure is changed for differing types of spray patterns;however, in each instance the orifice cross-section must be very small,for example, an equivalent diameter in the order of .011" to .018.

Inasmuch as the orifice size is very small, clogging of the orificebecomes a serious problem. Even with the high quality non-abrasive lightpigmented paints, the spray gun can usually be operated only for aboutan hour before cleaning of the gun is required. When nonabrasive heavypigmented paints are used, clogging of the orifice occurs in evenshorter periods of time, for ex ample, to 30 minutes. Heavy pigmentedabrasive paints will cause clogging almost immediately.

Hence it can be seen that poor operation occurs during the use of eventhe high quality non-abrasive light pigmented materials. It isimpractical to utilize the equipment for the heavy pigmented andabrasive materials. Many attempts to provide satisfactory filtering forthe various materials have been suggested over the years but so far asis known no commercially satisfactory solution has been provided priorto applicants improved filterspray gun construction. Applicant has founda filtering structure which, when combined in a particular manner with aspray gun, provides improved, commercially acceptable operation of thespray apparatus.

Applicants solution to this problem is far from obvious. It is wellknown in the art that the orifice of the spray tip must be placed inclose proximity to the control valve. As small a space as possible mustbe provided between the orifice inlet and the control valve outlet toprovide satisfactory operation. If this space is too large, the materialin the space, upon closure of the control valve, will drip from the endof the spray tip. Subsequent opening of the control valve causes a moreserious problem. In the event that the space is too large, the initialshock of high pressure material coming through the control valve intothe space causes material in the space to splatter on the surface beingcovered rather than to be directed in a fine spray pattern against thesurface. Hence, it is not possible to make changes in this space at willwithout expecting to encounter splattering problems.

Applicant has found that the use of a disk-like screen in a small spacebetween the spray gun orifice and the spray gun control valve extendsthe operation time prior to required cleaning from 1 hour to 2 or 3hours; however, clogging of the orifice under these circumstances nowappears to be caused primarily by the inability of screen materials towithstand the movement of the materials at high pressures therethrough.The screen ma terial was found to dimple and finally rupture. Uponrupture, the filtering action is lost and the orifice clogs inapproximately 1 hour as is the case without the filter.

This problem is even more serious when heavy pigmented materials andabrasive materials were used. The dimpling and rupture by heavypigmented materials was found to occur in periods as short as /21 hour.However, this would at least make the use of the apparatus feasible forthe heavy pigmented materials.

However, abrasive materials cause dimpling and rupture in intervals asshort as 3 and 4 minutes and therefore it was still impractical toutilize the apparatus for abrasive materials.

Applicant subsequently found that the simple expedient of securing asmall rivet to the central portion of the screen material generally inalignment with the control valve opening eliminated the dimpling andrupturing problem. It now becomes possible to utilize the apparatus forheavy pigmented materials and abrasive materials for periods in theorder of 2 hours without shutdown for cleaning. With this improvedstructure a completely acceptable answer was provided for the handlingof the major portion of the materials which are the non abrasive, smallpigmented type. With this latter type of paint, continuous operationwithout shutdown for cleaning can be assured for an 8-hour period. Sinceit is desirable to clean the spray gun at the end of a working day, 8hours of continuous operation is all that presently appears to berequired.

Applicant then discovered that the use of a fine cylindrical strainer inthe spray gun upstream of the control valve in combination with the finedisk screen filter downstream of the control valve providessignificantly im proved operation for the heavy pigmented and abrasivematerials. Continuous operation for periods in the order of 4-8 hours isnow possible for the heavy pigmented materials as Well as for abrasivematerials. In addition, since the cylindrical screen can be provided ata relatively low price, it is desirable to utilize it even for the smallpigmented materials.

It can therefore be seen that by the provision of two very inexpensiveelements, as simple solution to a very difiicult problem has beenprovided.

Accordingly, it is a primary object .of the invention to provide in aspray gun an improved filtering means for non-abrasive small pigmentedmaterials and also for heavy pigmented and abrasive materials.

A feature of this invention is the provision of a fine mesh disk-likescreen interposed between the orifice of a spray nozzle and a controlvalve with a strengthening rivet or its equivalent in the center portionof the screen generally in alignment with the control valve outlet.

Another feature of this invention is the provision of a cylindrical finescreen in the spray gun upstream of the control valve.

Other objects and features will be extended upon a perusal of thefollowing description taken in conjunction with the accompanying drawingin which:

FIG. 1 is a side elevation view of a spray gun incorporating applicantsimproved filter means;

FIG. 2 is a partial elevation view showing the improvement in section;and

FIG. 3 is a perspective view of the improved disk-like filter.

The spray gun I is of a generally conventional construction except asmodified by the improved filtering means. The gun includes a pistol-typehandle 2, a noz- Zle structure 3, and an actuating trigger 4. The nozzleassembly 3 includes a barrel 5 defining a material inlet 6 and amaterial chamber 7.

The barrel 5 carries a control valve seat assembly 8. The assembly 8includes a hollow screw 10 including a material passageway 12. Thedisk-like valve seat 14 is positioned transversely in the passageway 12and the screw 10 is swaged to firmly retain the seat.

A coupler 16 is screwed on to the barrel 5 and retains a nozzle 18 and adisk-like filter 2t] firmly against the screw 10.

The trigger 4 operates a needle valve element 22 in a well known manneragainst the force of a biasing spring (not shown). The spring urges theneedle valve element toward the left (FIG. 2) in sealing engagement witha valve opening 24 in the seat 14.

The nozzle 18 comprises a generally annular body 26 with a slot 28. Agenerally cup-shaped spray tip 30 having a central orifice 32 ispositioned in the body 26 with the orifice disposed axially at thecentral portion of the slot 28. A retainer ring 34 is pressed into thebody 26 to hold the element 30 in place.

The filter 20 includes a metallic supporting and spacing ring 36. Adisk-like piece of fine wire mesh 38 is suitably secured to the ring 36.The central portion of the screen carries a rivet 40. The ring 36 ispreferably made of a soft metallic material so that under assemblypressure it will give slightly to provide a reliable seal between thenozzle body 26 and the screw 10. In addition, the axial length of thering 36 is made as short as possible. This will assure a minimum amountof space between the valve seat 14 and the orifice 32 for reasonsdescribed earlier. Prior art devices incorporated a disklike nylonsealing element (not shown) having a central aperture interposed betweenthe screw and the body 26. It has been possible to substitute the filter20 for the nylon element without substantially increasing the spacebetween the orifice 32 and the valve seat 14 and at the same timeprovide a similarly reliable seal.

A second filter assembly 50 is secured to the barrel 5. The assembly 50includes a body 52, a filter 54, and a coupler 56 rigidly retaining thebody 52 and the filter 54 on the barrel 5.

The filter 54 comprises a cylindrical element 58. The element 58 has anoutwardly extending flange 60 at its upper end rigidly held betweenjuxtaposed shoulders on the body 52 and the coupler 56. Axially spacedperipheral milled slots 62 are provided on the wall of the element 58 todefine radial fluid inlets. A fine mesh screen 59 in the shape of acylinder is fitted over the outside periphery of the element 58. Thelower end of the element 58 is thickened at 64 to receive a screw 66which retains the screen 59 in place against the flange 60. The body 52has an inlet 68 and a chamber 70. The screen 59 is positioned radiallyinwardly from the inner peripheral wall of the body 52 to permit fluidflow from the chamber 70 through the screen and slots 62 into a chamber72 in the element 58. The chamber 72 connects with the spray gun inlet6.

During operation of apparatus utilizing the spray gun 1, a lubricantpump (not shown) supplies a material from the reservoir (not shown)under high pressure, for example in the order of 1500 p.s.i., to theinlet 68. This pressure is normally maintained at all times during use.The control valve trigger 4 is then actuated each time that it isdesired to spray an accessible surface. When the trigger is actuated,the high pressure material flows through the valve opening 24 throughthe screen 38 and the orifice 32.

While there has been described what is believed to be the preferredembodiment of the invention, it will be understood that various changesand modifications may be made therein; and it is contemplated to coverin the appended claims all such changes and modifications as fall withinthe true spirit and scope of the invention.

What is claimed is:

1. In a device for spraying liquid materials of the type in which aspray nozzle forms a small cross-section aperture to define a spraypattern and in which a valve positioned in close proximity to theaperture controls the flow of material under high pressure through anopening therein to the aperture, the improvement comprising thecombination therewith of a disk-like fine mesh screen between theaperture and valve, a central strengthening structure for the screengenerally in alignment with the valve opening, said structure beingspaced from the edges of the screen so that it is disposed entirelywithin the area of the screen, and a fine mesh screen upstream of thevalve.

2. In a device for spraying liquid materials of the type in which aspray nozzle structure forms a small crosssection aperture to define aspray pattern and in which a barrel structure connected to the nozzlestructure includes a valve positioned in close proximity to the aperturecontrols the flow of the material under high pressure through an openingtherein to the aperture, the combination therewith of a disk-like filterincluding an annular sealing ring compressibly held between the nozzleand barrel structures to provide a seal therebetween, a fine mesh screencarried at its edges by the ring between the aperture and the valveopening, and a central strengthening rivet supported solely by thescreen spaced from the edges thereof and generally in alignment with thevalve opening.

References Cited in the file of this patent UNITED STATES PATENTS873,680 Pearse Dec. 10, 1907 984,082 Edgerton Feb. 14, 1911 1,835,865Hansen Dec. 8, 1931 2,492,037 Freeman et al. Dec. 20, 1949 2,510,395Goodrie June 6, 1950 2,619,387 Cornelius et al. Nov. 25, 1952 2,625,437Huntington Jan. 13, 1953 2,705,663 Gilbreath Apr. 5, 1955 2,707,051Mailhot et al. Apr. 26, 1955 2,717,178 Cornelius Sept. 6, 1955 2,761,529Wisenbaugh Sept. 4, 1956 2,771,998 Holden Nov. 27, 1956 2,778,620Goodrie Jan. 22, 1957

